This invention relates to electronic musical instruments in which a single tone generating circuit is used for a plurality of channels on a time division basis to simultaneously produce a plurality of tones from the respective channels.
In order to permit chord performance using an electronic musical instrument, the electronic musical instrument has to be able to simultaneously produce a plurality of tones. To this end, it is thought to provide the electronic musical instrument with a plurality of tone generating circuits and permit a plurality of predetermined tones to be simultaneously produced from respective tone generating circuits specified by performance keys or to permit a single tone generating circuit to be used for a plurality of channels on a time division basis to simultaneously produce a plurality of tones from the respective channels. Either of these two methods can be used without any difficulty in a case where a plurality of simultaneously produced tones are of the same tone color. However, when at least one of the plurality of tones is different in tone color from the remaining tones, various problems are presented. In the case of the former method, it is possible to simply produce tones having different tone colors from respective tone generating circuits. On the demerit side, however, a great deal of hardware is necessary, leading to high cost. Also, with this method it is difficult to provide a compact and inexpensive electronic musical instrument. The latter method requires less hardware compared to the former method and permits construction of a compact instrument. However, when channels are switched in the time division basis operation, difficulties are involved in the control of switching a tone color over to another tone color, and an electronic musical instrument based on the latter method and having satisfactory performance has, as far as is known, not yet been realized.